Centrifugal gas separators are well known and are used in many different settings, to remove solids or liquids from air or from another gaseous intake stream. For example, in woodworking shops or sawmills, centrifugal gas separators are often used to remove sawdust and other airborne particles from the air in the work environment. Likewise, in certain agricultural applications such as the harvesting of hops for beer production or the harvesting of medical marijuana, a vacuum may be used to suck loose leaf material through openings in a tumbler, and a centrifugal gas separator may be used to remove the extracted leaf material from the air.
The two most common forms of conventional centrifugal gas separators are cyclonic separators and Thien separators.
A typical cyclonic separator consists of a vertical cylinder mounted above a vertical conical frustum (“cone”). The diameter of the cone is equal to that of the cylinder where they are joined, but progressively narrows as it descends downward from the cylinder, terminating at a circular opening at the bottom. A horizontal air intake near the top of the cylinder introduces a flow of dust-bearing air into the cylinder, in a direction generally tangential to the outer wall of the cylinder. The inside surface of the cylinder causes the incoming flow of dust-bearing air to rotate around the inside of the cylinder, as a result of which centrifugal force causes the dust particles to travel radially outward to the cylinder wall as they rotate around the cylinder. Gravity gradually pulls the rotating dust particles down into the cone, and they gradually descend to eventually exit through the bottom of the cone and into a collection receptacle. The cylinder has a disc-shaped top plate having a clean air opening surrounding the central axis of the cylinder. The clean air opening draws air out from an axially central volume of the top region of the cylinder. The rotation of the dust-bearing air in the cylinder forces the dust particles radially outward and gravity pulls the dust particles axially downward, so the air being drawn from the top central axial volume of the cylinder is generally free of dust, or at least is generally free of dust particles larger than the “cut point” of the separator, which defines the size of particle that will be removed from the stream with 50% efficiency.
A Thien separator is somewhat similar, insofar as it includes a vertical cylinder, an intake to direct a tangential flow of dust-bearing air to rotate around the inside wall of the cylinder, and a clean air opening defined through an axially central opening in a disc-shaped top plate of the cylinder. The Thien separator lacks the conical frustum section of the cyclonic separator. Instead, a disc-shaped bottom plate of the cylinder has a C-shaped or crescent-shaped aperture near the outer periphery of the disc. Dust-bearing air is introduced through the intake to rotate around the inside of the cylinder, and the resulting centrifugal force pushes the dust radially outward against the cylinder wall as it rotates. Gravity gradually pulls the dust particles downward as they rotate around the inside of the cylinder wall, until the dust particles eventually pass downward through the C-shaped aperture and into a collection receptacle.
The present inventors have perceived a number of disadvantages with conventional centrifugal gas separators.
For example, both Thien separators and the basic forms of cyclonic separators can only operate in a vertical orientation, because they require the force of gravity to cause the dust particles to exit from the separator. Although some manufacturers now offer complex solutions involving numerous additional components and additional airflow injections to allow horizontal operation of cyclonic separators, the added cost, complexity, energy consumption and maintenance demands of these additional components create new disadvantages which offset their capacity for horizontal operation.
Cyclonic separators are also very space-consuming. In their basic vertical form they are typically at least as tall as an adult person, and in their more complex horizontal form they tend to be even larger, though horizontally oriented.
Both cyclonic and Thien separators typically require many rotations of the dust-bearing air inside the cylinder before the dust is eventually separated. This long dwell-time is in itself disadvantageous, and also results in the further disadvantage that it is not difficult to saturate or overload cyclonic and Thien separators by introducing particulate material at a faster rate than it can be removed.